1. Field of the Invention
This invention relates to laundry detergent compositions having a high water-soluble alkaline carbonate builder content.
2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
Laundry detergent compositions comprising a water-soluble alkaline carbonate are well-known in the art. For example, it is conventional to use such a carbonate as a builder in detergent compositions which supplement and enhance the cleaning effect of an active surfactant present in the composition. Such builders improve the cleaning power of the detergent composition, for instance, by the sequestration or precipitation of hardness causing metal ions such as calcium, peptization of soil agglomerates, reduction of the critical micelle concentration, and neutralization of acid soil, as well as by enhancing various properties of the active detergent, such as its stabilization of solid soil suspensions, solubilization of water-insoluble materials, emulsification of soil particles, and foaming and sudsing characteristics. Other mechanisms by which builders improve the cleaning power of detergent compositions are probably present but are less well understood. Builders are important not only for their effect in improving the cleaning ability of active surfactants in detergent compositions, but also because they allow for a reduction in the amount of the surfactant used in the composition, the surfactant being generally much more costly than the builder.
While laundry detergents containing a relatively large amount of carbonate builder are generally quite satisfactory in their cleaning ability, the use of such carbonate builders often results in the problem of calcium carbonate precipitation, which may give rise to fabric encrustation due to the deposition of the calcium carbonate on the fiber surfaces of fabrics which in turn causes fabric to have a stiff hand and gives colored fabrics a faded appearance. Thus, any change in available carbonate built laundry detergent compositions which reduces their tendency to cause fabric encrustation is highly desirable.
The following prior art references may be considered relevant or material to the invention claimed herein.
U.S. Pat. No. 3,858,854, issued Jan. 7, 1975 to Win et al., discloses detergent compositions comprising a surfactant which may be anionic, monionic or amphoteric, or a mixture of two or more of such surfactants, a water-soluble builder salt which may be sodium carbonate or bicarbonate, and beads comprising an enzyme which may be a protease.
U.S. Pat. Nos. 4,265,790, issued May 5, 1981 to Winston et al.; 4,464,292, issued Aug. 7, 1984 to Lengyel; and 5,376,300, issued Dec. 27, 1994 to Bolkan et al., each discloses detergent compositions comprising an ethoxylated long chain alcohol and a sulfate of an ethoxylated long chain alcohol as a combination of nonionic and anionic surfactants, and over 70 wt % of anhydrous sodium carbonate (soda ash) as a detergent builder. These patents also teach that enzymes may be present in their compositions, and the Bolkan et al patent states that a carboxylic polymer, e.g. a copolymer of acrylic and maleic acids, may be included in the composition.
U.S. Pat. No. 5,308,530, issued May 3, 1994 to Aronson et al., discloses detergent compositions comprising a carboxylic polymer builder and anti-redeposition agent containing a C.sub.8 -C.sub.18 alkyl group, a calcium-sensitive enzyme which may be a protease, and a surfactant.